Friday, March 24, 2017

Retro Review: Garrett CM 20 Calculator



Retro Review:  Garrett CM 20 Calculator
 
Introduction

Is it Pac Man or is it a calculator?

I bet if Pac Man and Ms. Pac Man ever used a calculator, it is this one: the Garrett CM 20 calculator.  I received this calculator as a present from my good friend Chris Brame in Illinois.  Many thanks and appreciation, and it is hit with the household.

There is close to no information for the Garrett CM 20, only to find that model originated in 1973, predating the famous Pac Man game by seven years.  On the bottom label, the Garrett Comtronics Corporation is located in San Diego, California.  The CM 20 was made in the United States. 

The CM 20 is AC powered, with the power switch on the back of the calculator.




A Spherical Delight

The CM 20 comes has a spherical design.  Garrett also produced several calculators with a spherical design, the CM 25 and CM 35.  The CM 25 has memory functions. 

The keyboard on the CM 20 is just a delight; the keys are light to the touch and easy on the fingers.  Also, the keys are responsive. 

Check out the display, the digits are orange! 



The A/B and % Keys

The CM 20 is a real basic four function calculator, without memory or a square root key.  However, the CM 20 has an A/B key, which works as a “Last X” key (think scientific keystroke programmable calculators from Hewlett Packard).  After a pending operation completes (+, -, *, or ÷), press the A/B key to recall the last number entered before completing the operation.  For example:

6 [ + ] 3 [ = ]   (Display:  9)  Pressing [A/B] recalls 3 (and puts 9 in the temporary register)

3 [ + ] 6 [ = ]   (Display:  9)  Pressing [A/B] recalls 6 (and puts 9 in the temporary register)

75 [ ÷ ] 15 [ = ]  (Display: 5)   Pressing [A/B] recalls 15.

And so on.

The percentage key works a little bit different from most four-function calculators.  On the CM 20, you are required to press the equals key to complete the operation.  To find out a percentage of a number, enter the base, press any of the arithmetic keys, the percentage and the % key.  To illustrate:

25 [ + ] 15 [ % ]  (Display: 3.75) [ = ] (Display 18.75 = 25 + 15%)

25 [ - ] 15 [ % ]  (Display: 3.75) [ = ] (Display 21.25 = 25 – 15%)

25 [ * ] 15 [ % ]  (Display: 3.75) [ = ] (Display 93.75 = 25 * 3.75 = 25 * (25 * 15%))

25 [ ÷  ] 15 [ % ]  (Display: 3.75) [ = ] (Display 166.66666 = 25 / 0.15)

25 [ + ]/[ - ]/[ * ]/[ ÷ ] 15 [ % ] Stop.  (Display:  3.75 = 25 * 15%)

Final Verdict

This calculator is going to be on my desk for a long time.  I love the retro 1970s design and the spherical shape of the calculator.  Thank you Chris!

Eddie

This blog is property of Edward Shore, 2017





Wednesday, March 22, 2017

HP 15C: Pythagorean Triples



HP 15C:  Pythagorean Triples

This program calculates the Pythagorean triple (A, B, C) such that A^2 + B^2 = C^2 by the formulas:

A = K * (M^2 – N^2)
B = K * (2 * M * N)
C = K * (M^2 + N^2)

The conditions are M, N, and K are all positive integers where M > N. 
Store M into memory 0, N into memory 1, and K into memory 2.  A, B, and C are stored in memories 3, 4, and 5, respectively.  If no such combination can be found, a single zero (0) is returned.

Step
Key
Code
001
LBL A
42, 21, 11
002
RCL 1
45, 1
003
RCL 0
45, 0
004
X≤0
43, 10
005
GTO 0
22, 0
006
RCL 0
45, 0
007
X^2
43, 11
008
RCL 1
45, 1
009
X^2
43, 11
010
-
30
011
STO 3
44, 3
012
LST X
43, 36
013
2
2
014
*
20
015
+
40
016
STO 5
44, 5
017
RCL 0
45, 0
018
RCL* 1
45, 20, 1
019
2
2
020
*
20
021
STO 4
44, 4
022
RCL 2
45, 2
023
STO* 3
44, 20, 3
024
STO* 4
44, 20, 4
025
STO* 5
44, 20, 5
026
RCL 3
45, 3
027
X^2
43, 11
028
RCL 4
45, 4
029
X^2
43, 11
030
+
40
031
RCL 5
45, 5
032
X^2
43, 11
033
-
30
034
X=0
43, 20
035
GTO 1
22, 1
036
LBL 0
42, 22, 1
037
0
0
038
RTN
43, 32
039
LBL 1
42, 21, 1
040
RCL 3
45, 3
041
R/S
31
042
RCL 4
45, 4
043
R/S
31
044
RCL 5
45, 5
045
RTN
43, 32

Example:  Input:  R0 = M = 4,  R1 = N = 1, R2 = 2.   Output:  30, 16, 34

This blog is property of Edward Shore, 2017.

Retro Review: Garrett CM 20 Calculator

Retro Review:   Garrett CM 20 Calculator   Introduction Is it Pac Man or is it a calculator? I bet if Pac Man and Ms. ...